In this study the CROPWAT method was used to evaluate the crop water requirements of six selected agricultural districts, Kiambu, Makueni, Kwale, Laikipia, Vihiga and Migori, distributed across six provinces of Kenya: Central, Eastern, Coast, Rift Valley, Western and Nyanza respectively. These districts were selected to reflect the diversity of the country’s agro-ecological zones. The objective was also to evaluate the crop water requirements, crop responses to climate change/variability, and levels of crop productivity across the different agro-ecological zones. The results show that an increase in temperature increases the percentage change in crop water use. The changes in crop water use from the output of the CCCM scenario were lower than those from the GFDL3 for all the districts studied. Within a set of temperature change scenarios, changes in rainfall did not appear to change the amount of water used by crops. The effect of rainfall changes could, however, be implicit in the demonstrated decrease in the amount of irrigation water needed following an increase in the amount of rain. Patterns of irrigation water requirement and field water supply deviated from the above mentioned trend in response to temperature changes. In general, increasing rainfall by 20% from the original long-term mean for each of the two models decreased the irrigation water requirement for the crops studied, whereas decreasing rainfall by 20% increased it. This is likely to be the case because the increase in rainfall satisfies a greater portion of crop water requirement so that less irrigation water is required. In general, field water supply was higher during climate change scenarios associated with lower rainfall amounts (-20% of the original long-term mean).